The Met is investigating footage which appears to show a man being repeatedly struck on the head by officers while on the ground in an incident in east London on Saturday evening.
Videos shared on social media showed members of the public arguing with police during an arrest in Kingsland High Street, Dalston.
Protesters could be heard shouting “let them go” in response to those who had been detained by officers.
One video appears to show officers standing beside a police van outside Kingsland Shopping Centre and a protester struggling before seemingly being struck in the head while on the floor.
The Metropolitan Police said officers were carrying out a pre-planned operation "targeting e-scooters and moped-enabled crime" when they stopped a man who they said was wanted for immigration offences.
As officers arrested the man, a crowd of people gathered in an attempt to stop them and a number of officers were assaulted during the incident, officers said.
The force added "any footage showing use of force" was being "reviewed" by the Directorate of Professional Standards.
In a statement, the force said: "We are aware of a number of videos on social media filmed during the incident.
"We would urge people to remember that such videos rarely provide a full and accurate picture of what is taking place.
"Police officers are aware that any use of force must be proportionate and reasonable, and they understand that their actions will be scrutinised as they go about their work and that they will be held to account where appropriate."
Nine people were arrested for offences including violent disorder. They remain in police custody.